Abstract
In arid and semi-arid regions, identifying and monitoring of soil alkalinity and salinity are in urgently need for preventing land degradation and maintaining ecological balances. In this study, physicochemical, statistical, and spectral analysis revealed that potential of hydrogen (pH) and electrical conductivity (EC) characterized the saline-alkali soils and were sensitive to the visible and near infrared (VIS-NIR) wavelengths. On the basis of soil pH, EC, and spectral data, the partial least squares regression (PLSR) models for estimating soil alkalinity and salinity were constructed. The R2 values for soil pH and EC models were 0.77 and 0.48, and the root mean square errors (RMSEs) were 0.95 and 17.92 dS/m, respectively. The ratios of performance to inter-quartile distance (RPIQ) for the soil pH and EC models were 3.84 and 0.14, respectively, indicating that the soil pH model performed well but the soil EC model was not considerably reliable. With the validation dataset, the RMSEs of the two models were 1.06 and 18.92 dS/m. With the PLSR models applied to hyperspectral data acquired from the hyperspectral imager (HSI) onboard the HJ-1A satellite (launched in 2008 by China), the soil alkalinity and salinity distributions were mapped in the study area, and were validated with RMSEs of 1.09 and 17.30 dS/m, respectively. These findings revealed that the hyperspectral images in the VIS-NIR wavelengths had the potential to map soil alkalinity and salinity in the Songnen Plain, China.
Highlights
Soil alkalinity and salinity are the primary causes of land desertification, which usually occurs in irrigated farmland and grassland in arid and semiarid regions
This study explored the potential of assessing the soil alkalinity and salinity in the northern Songnen Plain with a hyperspectral image in a black soil region of China
By using partial least squares regression (PLSR) models, we conducted a good prediction among soil potential of hydrogen (pH), electrical conductivity (EC) and hyperspectral imager (HSI)-like spectral bands with R2 values of 0.77 and 0.48, respectively
Summary
Soil alkalinity and salinity are the primary causes of land desertification, which usually occurs in irrigated farmland and grassland in arid and semiarid regions. Soils in dry lands worldwide, including those in the United States, China, Hungary, and Australia, suffer desertification and land degradation [2]. The total area of saline soil in China is 3.6 × 107 ha [3], approximately 9% of which is in the Songnen Plain [4]. Located in the central part of northeastern China, the Songnen Plain is composed of saline-alkali soils that are mainly due to soda [5]. Alkaline and slightly saline Grey white color. Brown color flats near playas and pools
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